Metal battery, such as a lithium air battery or more precisely called a lithium oxygen battery since the most widely investigated reactant is oxygen instead of air, is an attractive choice for future energy storage due to its high theoretical energy density of 7987 Wh/L, three times higher than the currently available lithium ion battery.
The reaction of interest on the cathode of the lithium oxygen battery is the reduction of oxygen, followed by reaction with lithium. Although the exact reaction mechanism is still under
Investigation, recent experiments indicate that a two-step one electron electrochemical reaction might be the dominating process, and the formation of reduced oxygen occurs on the electrode surface instead of in the electrolyte solution. The proposed reaction scheme is described in Scheme 1 as follows. The * symbolizes the surface reactions.2Li↔2(Li++e−) (anode)Li++e−+O2*↔ LiO2* (cathode)Li++e−+LiO2*↔ Li2O2* (cathode)  Scheme 1
Judging by these proposed reactions, besides the availability of lithium ions, another factor that is necessary for the reactions to occur is the availability of oxygen in the cathode. Oxygen accessibility is governed by the diffusion of oxygen and the amount of dissolved oxygen in the system.
In the case of a metal air (or metal oxygen) battery, an electrolyte with a high amount of dissolved oxygen is therefore desirable.